First the man grows out a huge bush. 70's style, so if standing on your head it would look like a hasidic jew "beard/nose" combo.
Then you shave it off and place it in a ziploc bag keeping it in close proximity to the next location of sexual promiscuity.
So the next time you're barebacking a chick from behind pull out just in time to unleash your jizzum all over the female buttocks.

Quickly grab the ziploc and dump contents all over said jizzum. wipe it in nice and good then jump on her back with enough forward momentum that your propelled off the bed on your makeshift flying broom (nimbus 2000)

Spencer: Why is your girlfriend so mad?

Kevin: She found out she sucks at flying.

Spencer: Airplanes????

Kevin: Nah, I gave her The Harry Potter and her ass barely cleared my dresser.

Occurs when, during a three-some, a female is jacking off a male. Right before he's ready to culminate, she yells "Alakazam," quickly turns the cock and, in a wand-like motion, yanks it so it blows all over the third member.

before a guy and girl have sex a friend hides in the closet in a wizard costume when the guy and girl are doing it or after the fried proceeds out of the closet and screams 10 points for griffindor and then runs out